Sintered hard compositions



United States Patent SINTERED HARD COMPOSITIONS Edward W. Goliber, Royal Oak, 'Mich assiguor to General Electric .tlompany, a corporation of New York No Drawing. Application January 4, 1955 Serial No. 479,861

3 Claims. (Cl. 29--182.5)

This invention relates to hard refractory compositions produced by powder metallurgy from pulverulent mixtures of alumina and lower oxides or suboxides of titanium and from pulverulent mixtures of the aforesaid two ingredients and chromium. Lower oxides or suboxides of titanium as used herein refer to oxides of titanium containing less oxygen than is present in a normal titanium dioxide and includes titanium-oxygen solid solutions containing as little as five Weight percent oxygen.

The need for materials having high strength and high hardness, as well as general chemical inertness, is ever increasing and of major importance in present industrial applications. Such materials are extremely useful in manufacturing cutting tools, extrusion and drawing dies, critical wear parts, etc.

It is known that the lower oxides or suboxides of titanium, for example, those approximating titanium monoxide in composition, are hard substances. However, these materials by themselves lack strength and are much too brittle for practical use. In my copending application, Serial No. 432,934, filed May 27, 1954, assigned to the assignee of the present invention, I have disclosed that the extreme brittleness and fragility of titanium suboxides alone can be overcome by pressing and sintering pulverulent mixtures of titanium suboxides and chromium, the resulting products being strong, hard and chemically inert.

It now has been found that extremely hard and comparatively strong materials can be obtained by sintering intimate mixtures of pulverulent titanium suboxides and alumina. Not only are these compositions stronger than the titanium suboxides alone, but they also otter advantages over sintered alumina in that they are electrically conductive, stronger and can be sintered at somewhat lower temperatures. g

It also has been found that the addition of chromium to the foregoing compositions improves their strength substantially with some sacrifice in hardness. Unexpectedly, the resulting compositions generally are both harder and stronger than the compositions prepared from titanium suboxides and chromium disclosed in my aforementioned copending application.

The amounts of the components employed in preparing the compositions of the present invention may vary atomic ratio 2,872,726 Patented Feb. 10, 1959 ICC specifically, the oxygen content may vary such that the lies between .25 and 1.4.

may be obtained when pulverulentchromium, titanium suboxides and alumina are intimately mixed and sintered in proportions such that the final sintered body contains chromium up to 60 weight precent. A preferred chromium content lies between about 25 and 50 weight percent. Although theaddition of chromium in amounts between 0 and 25 percent, by weight, does not substantially improve the strength'of the materials of the invention, compositions contained within these limits are also intended within the scope of the invention. The titanium and aluminum may be present in proportions such that the Al/Ti atomic ratio lies between about 0.8 and about 5. The oxygen content may vary such that it is present in an amount equivalent to the formation of A1 0 with an additional amount present equivalent to an O/Ti atomic ratio of between .6 and 1.3. the oxygen content may vary such thatthe atomic ratio O-3/ 2 Al in a single material. These limits are critical since only compositions within these limits display the desired hardness as well as the desired strength. The criticality of within certain limits. For example,'extre1nely hard and comparatively strong substances may be produced from pulverulent titanium suboxides and alumina mixed and sintered in proportions such that the final sintered body contains aluminum and titanium in an Al/Ti atomic ratio of between .8 and 20. The oxygen content may also vary and may be present in an amount equivalent to that required for the complete oxidation of aluminum to A1 0 with an additional amount present equivalent to an O/Ti atomic ratio of between .25 and 1.4, More these limits is best illustrated by the examples hereinafter found.

In one embodiment of this invention, the pulverulent mixed oxides used in preparing the compositions of the present invention may be conveniently prepared by reacting an intimate mixture of aluminum and titanium dioxide in the desired proportions. In order to prepare some compositions, it may be necessaryto admix titanium metal powder or alumina, as the case may be. powders may be mixed and caused to react by heating from about 1000 C. to about 1400 C. in a hydrogen atmosphere. The reacted briquettes, being porous, are

readily crushed or milled to a-fine powder. Because the initial metal powders are somewhat oxidized and because some oxidation occurs during processing, a slightly less amount of oxygen is added in the form of oxides than In another embodiment of this invention, the titanium I suboxides employed may be prepared from an intimate mixture of titanium metal powder and titanium dioxide mixed in predetermined proportions. The resulting powder is then reacted and crushed as described above;

More specifically,

Iron, for example, may be present.

These invention. For example, sintering temperatures may be varied from about 14-50 to 1650" C. and inert atmospheres other than hydrogen may be employed for the sintering. Additionally, the usual procedures and techniques employed in powder metallurgy and ceramics for molding or processing of powders generally are applicable and the compositions may be varied to obtain variations in properties as desired.

The compositions of the present invention have a wide range of utility. Due to their unique properties, they may be used in the fabrication of cutting tools, extrusion and drawing dies, critical furnace parts, critical wear parts, etc. 7 i

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A sintered, strong and hard composition consisting essentially of a lower oxide of titanium alumina and chromium, the chromium being present in percentages up to about 60 percent, by weight of the composition, the remainder being titanium, aluminum and oxygen in proportions such that the aluminum titanium atomic ratio is from about .8 to about 5, and the oxygen content .is such that the atomic ratio,

O-3/2 Al lies between .6 and 1.3.

3. A sintered, strong and hard composition consisting essentially of a lower oxide of titanium, alumina and chromium, the chromium being present in percentages of from to about SOpercent, by Weight of the com-- position, the remainder being titanium, aluminum and oxygen in proportions such that the aluminum titanium atomic ratio is from about .8 to about 5, and the oxygen content is such that the atomic ratio,

' O--3/ 2 Al lies between .6 and 1.3.

References Cited in'the file of this patent UNITED STATES PATENTS 2,252,981 2,431,660 Gaudenzi Nov. 25, 1947 2,698,990 Conant Jan. 11, 1955 2,783,530 Conant Mar. 5, 1957 FOREIGN PATENTS 910,811 France Feb. 18, 1946 676,441

Ridgway Aug. 19, 1941 Great Britain July 30, 1952 i UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Nou 2,872,726 February 10, 1959 Edward W, Goliber Column 6, line 12, after "from." insert about Signed and sealed this 29th day of September 1959o (SEAL) Attest:

KARL H, AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Noo 2,872,726 February 10, 1959 Edward Wa Goli'ber Column 6, line 12, after "from" insert about Signed and sealed this 29th day of September 1959a (SEAL) Attest:

KARL AXLINE ROBERT C. WATSON Attesting Oflicer Commissioner of Patents 

1. A SINTERED, STRONG AND HARD COMPOSITION CONSISTING ESSENTIALLY OF A LOWER OXIDE OF TITANIUM ALUMINA AND CHROMIUM, THE CHROMIUM BEING PRESENT IN PERCENTAGES UP TO ABOUT 60 PERCENT, BY WEIGHT OF THE COMPOSITION, THE REMAINDER BEING TITANIUM, ALUMINUM AND OXYGEN IN PROPORTIONS SUCH THAT THE ALUMINUM TITANIUM ATOMIC RATIO IS FROM ABOUT 8 TO ABOUT 5, AND THE OXYGEN CONTENT IS SUCH THAT THE ATOMIC RATIO, 